it seems to me that not all lines qualify as lines for a breakpoint, though one is allowed to set a breakpoint.
Date(TempDate) AS KeyDate
drop Table TempCalendar;
In my script, only breakpoints before "Calendar:" and before "drop ..." had an effect on debugger.
There is a similar behaviour in other scripting IDEs, but most of the time they prevent you from dropping a breakpoint on these lines.
Please try if you get an effect on any line.